Oxcarbazepine is chemically known as 10-oxo-10,11-dihydro-5H-dibenz[b,f]azepine-5-carboxamide and represented by the following structural formula:

Oxcarbazepine is commercially available as TRILEPTAL®, which has been approved by the United States Food and Drug Administration for use in the treatment of epilepsy and use as monotherapy or adjunctive therapy in the treatment of partial seizures in adults and as monotherapy in the treatment of partial seizures in children.
U.S. Pat. No. 3,642,775 assigned to Ciba-Geigy Corporation, claims Oxcarbazepine specifically and discloses the process for the preparation of Oxcarbazepine, wherein 10-methoxy-5H-dibenz[b,f]azepine is reacted with phosgene gas to give 10-methoxy-5H-dibenz[b,f]azepine-5-carbonyl chloride and ammonolysis of the resultant compound to give the amide followed by hydrolysis to give Oxcarbazepine.
U.S. Pat. No. 5,808,058 assigned to Trifarma S.r.l., claims a process for the preparation of Oxcarbazepine by carbomylating 10-methoxyiminostilbene with sodium or potassium cyanate in the presence of strong non-aqueous acid, followed by mild aqueous acid hydrolysis of the methoxy group.
U.S. Pat. No. 6,670,472 B2 assigned to Max India Limited, claims a process for the preparation of Oxcarbazepine, which comprises reacting 10-methoxyiminostilbene with cyanic acid generated in situ by reaction of an alkali metal cyanate and a mild aromatic acidic reagent such as benzoic acid, the obtained 10-methoxycarbamazepine may then be hydrolyzed to form Oxcarbazepine. The major disadvantage of this process is the reported yields are very low, of about 28-49%.
US 2005/0203297 A1 assigned to Glenmark Pharmaceuticals, claims a process for the preparation of 5H-dibenz[b,f]azepine-5-carboxamide by reacting 5H-dibenz[b,f]azepine with one or more alkali or alkaline-earth cyanates in the presence of one or more unsaturated dicarboxylic acid. But, this process involves number of purification.
In the prior art processes, cyanic acid is generated by reaction of alkali metal cyanates in the presence of acid with or without electron with-drawing groups. The starting material (10-methoxy iminostilbene) is sensitive to acids, due to more acidic nature of the acid the starting material may decompose and more degradation impurities are obtained in the prior art processes. We identified a new class of acid compounds i.e., α-hydroxy acids, where the hydroxyl is a electron releasing group at α-position, this influences the basicity of the acid. So these acids are less acidic than the reagents claimed in the prior art and less by-products are expected in the reaction.
According to the prior processes, strong acids are used for both the carbomylation reaction and the hydrolysis reaction. These acids are actively involved in ether hydrolysis to form substantial quantities of byproducts, i.e., oxo-iminodibenzyl or lead to degradation of the product and result in substantial quantities of impurities. Due to formation of impurities, repeated purifications in different solvents are needed to give the desired quality of the final product.
The major disadvantage as per prior art processes is incomplete hydrolysis of the starting material. According to the prior art processes, 10-methoxycarbamazepine content, while hydrolysis reaction is around 3%. The removal of 10-methoxy carbamazepine from the final API requires a number of purifications in different solvents. Whereas, the present invention provides a hydrolysis reaction in which the starting material content is less than 1%, preferably less than 0.5%. Therefore the present invention provides Oxcarbazepine with improved yields and quality. The present invention also provides the API with good color when compared to the product obtained by prior art processes.
Therefore, there is a need to develop a process for the preparation of Oxcarbazepine, which is economical and results in high yields. The present invention will overcome the deficiencies of the prior art and provide a higher yielding, cost-effective and scalable process for the commercial production of highly pure Oxcarbazepine.